CA1319330C

CA1319330C - Brake device

Info

Publication number: CA1319330C
Application number: CA000564149A
Authority: CA
Inventors: Kouhei Yamatoh; Masami Ogura
Original assignee: Honda Motor Co Ltd
Current assignee: Honda Motor Co Ltd
Priority date: 1987-04-17
Filing date: 1988-04-14
Publication date: 1993-06-22
Anticipated expiration: 2010-06-22
Also published as: DE3864918D1; US4860859A; EP0296703A1; EP0296703B1; JPS63266228A

Abstract

Abstract of the Disclosure A brake device comprising an ultrasonic motor having a rotor rotatable by an elastic traveling wave generated by a piezoelectric vibrator on a stator of the motor, and torque converting means for converting a rotating torque produced by said ultrasonic motor into a pressing force for pressing a friction member against a member to be braked, which is transmitted to said friction member.

Description

13193~0 The present invention relates to a brake device having an electric motor employed as a drive source for pressing a friction member against a member to be braked, thereby producing a braking force.

Heretofore, an electric hrake device having a wound-rotor type motor used as drive source for braking automobiles has been proposed. In such an electric brake device, in order to obtain a necessary and sufficient braking torque, the wound-rotor type motor used has to be large in size and heavy in w~ight. Therefore, the electric brake device presents an installation problem and poses a disadvantage with respect to a battery power supply owing to its large power consumption.
In view of the above difficulties, it is an object of the present invention to provide a brake device driven by an electric motor and suitable for use in an automobile, in particular, the brake devics being small in size, light in weight, and capable of producing necessary and sufficient braking forces with a small power consumption.

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According to a first aspect of the invention there is provided a braka device arranged to press a friction member against a member to be braked, thereby applying a bra~.ing action to said member to be braked, said brake device comprising; an ultrasonic motor including a stator, a rotor and a piezoelectric vibrator mounted on the stator to generate an elastic travelling wave to drive said rotor; and torque converting means for converting a rotating torque produced by said ultrasonic motor into a pressing force for pressing the friction member against the member to be braked, said pressing force being transmitted to said friction member.

According to a second aspect of the invention there is provided a brake device arranged to press a friction member against a member to be braked thereby applying a braking action to said member to be braked, said brake device comprising an ultrasonic motor for producing a rotating torque; and torque converting means for converting a rotating torque produced by the ultrasonic motor into a pressing force for pressing the friction member against the mem~er to be braked, said pressing force being transmitted to said friction member.

The preferred embodiment of the present invention comprises a brake device comprising an ultrasonic motor having a stator, a rotor and a piezoelectric vibrator mounted on said stator to produce an elastic travelling wave to rotate said rotor, and torque converting means for converting a rotating torque produced by said ultrasonic motor, through a ~peed reducing gearing ~or increasing a torque and/or a linear converting mechanism for converting a rotating torque to a linear :-, propulsion force, into a pressing force for pressing a ~riction member against a member to be braked, said pressing force being transmitted to said friction member.

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Reference is now made to the accompanying drawings, in which:

FIG. 1 is a cross-sectional view of a brake device according to an embodiment of the present invention;

FIG. 2 is a cross-sectional view of a brake device according to another embodiment of the present invention; and FIG. 3 is a side elevational ~riew of a drum brake in the embodiment of FIG. 2.

Embodiments of the present invention will 3a-.:: , .... ~

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hereinafter be described in detail with reference to the accompanying drawingP..
FIG. 1 shows an embodiment of the present invention which is applied to a di~c-type brake device, which include~ a brake pad 2 arrangad at one side o a di~c rotor 1 of an automobile wheel and a brake pad 3 mounted on a caliper 4, 80 that the disc rotor 1 is 3andwiched between the brake pads 2 and 3 and the brake pad 2 is pres~ed against one side of the disc rotor to produce braking action. An ultrasonic motor 5 i8 mounted on -the caliper 4. The ultrasonic motor ha~
output shaft 6, the rotating ~peed of which is reduced by a planetary gear mechanism 7 for an increased torque and then the rotation of the output shaft 6 i~
transmitted to a linear converter mechanism 8 by which the rotation is converted into a linear movement that pre~es a pre~sure plate 9 on which the brake pad 2 is mounded against the di~c rotor 1.
The planetary gear mechani~m 7 comprise~ a first ~un gear 71 mounted on the output ~haft 6, a planet gear 72 di~posed between and me~hing with the ~un gear 71 and an internal gear 73 attached to the caliper 4, a second sun gear 75 mounted on the planet gear 72 by a ~lanet carrier 74, a planet gear 76 disposed between and me~hing with the ~econd sun gear 75 and the 3 ~

internal gear 73, and a coupling gear 78 mounted on the plane-t gear 76 by ~ planet carrier 77.
The linear converter mechanism 8 comprises a hollow ball nut 81 rotatably mounted in the caliper 4 by bearings 2B, 29, and a ball screw 82 threadedly engaged in the ball nut 81 with balls 83 therebetween and axially movable in response to rotation of the ball nut 81. The ball nut 81 has a gear 84 formed an one end thereof wich is held in mesh with a coupling gear 78 of the planetary gear mechanism 7, 80 that the rotation of the planetary gear mechanism 7 can be tran~mitted to the ball nut 81. The pressure plate 9 i3 fi~ed to the ball screw 82.
A controller 10 reads a signal from a potenti.ometer 12 which is indicative of the amount of depre~sion of a brake pedal 11. The controller 10 then applies a motor drive voltage controllad to produce a torque dependent on the amount of depre~ion of the brake pedal 11 to the ultrasonic motor 5. Denoted at 13 is a power supply.
: In operation, when the brake pedal 11 is depres~ed, the ultra~onic motor 5 i~ enargiæed under the control of the controller 10 dependent on the amount of depression of the brake padal 11. The speed of rotation of the output shaft 6 is reduced by the`

3 a planetary gear mechanism 7 for an increased torque.
Then, the rotation from the output shaft 8 is converted by the linear converter mechanism 8 into a linear movement that causes the pressure plate 9 to press the brake pad 2 against the di~c rotor 1. The disc rotor 1 i~ clamped between the brake pads 2, 3 to produce braking forces commensurate with the amount of depre~sion of the brake pedal 11.
FIG. 2 shows another embodiment of the prasent invention which is applied to a drum-type brake device.
The brake device includes an ultrasonic motor 5 mounted on a back plate 14. Tha ultrasonic motor 5 has an output shaft 6, the rotationg ~peed of which is reduced by a planetary gear mechanism 7 for an increased torque. The rotation is then transmitted through a rotatable shaft 15 coupled to splines 79 on the output member of the planetary gear mechanism 7 to rotate an eccentric camshaft 18 which spreads out lining plates 17 in a drum brake 16 (FIG. 3). The lining plates 17 have rollers 30 engaging a cam 19 of the eccantric camshaft 18 80 that the lining plates 17 can easily be ~pread outwardly by the cam 19. The planetary gear mechanism 7 i8 of substantially the same ~tructure a~ that of the planetary mechanism shown in FIG. 1. Therefors, identical parts of the planetary :

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gear mechani~m 7 are denoted by identical reference numerals in FIG. 1.
In operation of the brake device of FIGS. 2 and 3, when the brake pedal 11 i8 depressed, the ultrasonic motor 5 is engegized under the control of the controller 10 dependent on the amount o depre3~ion of the brake pedal 11. The ~peed of rotation of the output shaft 6 is reduced by the planetary gear mechanlsm 7 for an increasad torque. Then, the rotation causes the ~haft 15 to rotate the eccentric camshaft 18 through a predetermined angle, whereupon the cam 19 spread~ the lining plates 1'7 outwardly to press linings 20 against a drum surface 21, thereby generating braking forces commensurate with the amount of depression of the brake pedal 11. The drum brake 16 shown in FIG. 3 has an automatic adjuster for k~eping the clearance between the linings 20 and the drum surface 21 at a constant level a8 the linings 20 are worn. Denoted at 22 i~ ~uch an adjuster, 23 an anchor pinl 24 return spriny~ for the lining plates 17, 25 an overload spring, and 26 a strut.
~ As descrivsd above, the brake device of the present invention employs an ultrasonic motor 5 as a drive source for effecting braking operation~ since the moment of inertia of the rotor of the ultrasonic ~3~9~3~

motor 5 is s~all, highly accurate braking forces can be produced which are highly responsive to the depression of the brake pedal 11, with the output torgue being precisely controlled dependent on the amount of depression of the brake pedal 11.
The ultrasonic motor 5 it~elf, serving as a drive 80urce for generating neces~ary and sufficient braking torque, is smaller and lighter than the ordinary wound-rotor type motor, and can appropriately be in~talled in position. The ultrasonic motor can produce a large braking torque with a small power consumption, and hence i~ advantageous for use with a battery power 8Upp ly.
When the ultrasonic motor 5 is de-energized, it produces a large retentive torque, preventing the output shaft from becoming free as is the case with the ordinary wound-rotor type motor. It i~ thus possible to arrange -the brake device to pravide a parking brake function when the power supply is cut off.
Although not shown, the speed of rotation of the disc rotor 1 may be detected by a rotation sensor, and the speed of travel of the automobile is detected by a ~peed sensor. The controller 16 may read output signal~ rom these senQors, respectively, and determines a slip rate of the automobile according to a ~31~

predetermined formula. If the determined slip rate i8 higher than a preset threshold, thsn the controller 10 may determine that the automobile is skidding. In this manner, an anti-lock braking capability may be provided for turning on and off the ultrasonic motor 5 to effect pumping brake action under the control of the controller 10.
It will be undrstood that the brake device of the invention employs an ultra~onic motor as a brake drive source, and the tor~ue of the ultrasonic motor is effectively converted. The brake device as a whole is small in size and light in weight, and can procduce necessary and ~ufficient braking forces with a small power consumption. The brake device is also capable of well ccntrollable and highly responsive braking control.

Claims

1. A brake device arranged to press a friction member against a member to be braked, thereby applying a braking action to said member to be braked, said brake device comprising;
an ultrasonic motor including a stator, a rotor and a piezoelectric vibrator mounted on the stator to generate an elastic travelling wave to drive said rotor; and torque converting means for converting a rotating torque produced by said ultrasonic motor into a pressing force for pressing the friction member against the member to be braked, said pressing force being transmitted to said friction member.

2. A brake device according to claim 1, in which said torque converting means includes a speed reducing gearing for increasing a torque and a linear converting mechanism for converting a rotating torque to a linear propulsion force, which is used to press a brake pad against a disk rotor of a disk-type brake device.

3. A brake device according to claim 1 in which said torque converting means includes a speed reducing gearing for increasing a torque and an eccentric camshaft driven by a rotating torque of the speed reducing gearing, said eccentric camshaft having a cam thereon which is arranged to spread out lining plates of a drum-type brake device.

4. a brake device according claim 2 or 3, in which the speed reducing gearing is a planetary gear mechanism.

5. A brake device according to claim 2, in which said linear converting mechanism includes a hollow ball nut rotatably mounted in a caliper of the brake device by means of a bearing and a ball screw threadedly engaged in said ball nut for axial movement by rotation of said ball nut.

6. A brake device according to claim 1, including means for detecting an amount of depression of a brake pedal to produce a signal indicating the amount of depression, and a controller for controlling the ultrasonic motor to produce a braking force dependent upon the amount of depression of the brake pedal in accordance with said signal.

7. A brake device according to claim 1, including means for detecting a skid sate of a vehicle to produce a skid state indicating signal, and a controller for controlling the ultrasonic motor to intermittently drive said motor in accordance with said skid state detecting signal, thereby effecting pumping braking action.

8. A brake device arranged to press a friction member against a member to be braked thereby applying a braking action to said member to be braked, said brake device comprising an ultrasonic motor for producing a rotating torque; and torque converting means for converting a rotating torque produced by the ultrasonic motor into a pressing force for pressing the friction member against the member to be braked, said pressing force being transmitted to said friction member.